Both of these (along with the French for “worldly boredom”, ennui) come from the Latin inodiare, meaning, “to hate”. The Latin in- adds emphasis to the odium, Latin for “hate”.
We can see the parallels in all with the open vowel, followed by the -n-, followed by a -y- sound, although in Spanish the -y- sounds (and its corresponding -x- and -sh- variations) often turned into the -j- sounds, as it did here. Thus, the a-n-y maps to the e-n-j.
Hatred, then, dissipates and weakens over time. In English, hatred weakens into mere annoyance. In Spanish, hatred weakens into just anger, enojo. And, best of all, hatred in French weakens into a world-weary boredom of ennui.
Chief, and the Spanish for the same, Jefe, both come from the same root: the French chef, which means the same.
But this is odd as they sound so different! How are they related?
It’s not obvious, but it’s easy once you understand the pattern: The Latin sound “sh” and very similar sounds (such as the “ch” and “sy”) almost always became a “j” in Spanish. Like syrup and jarabe. Not obvious!
Flojo comes from the Latin fluxus, meaning the same as the Spanish. From fluxus, we get a bunch of English words, including: fluent, fluid, fluctuate and even (via fluent) affluent and influence. We also get the more fun flush and the most obvious flux (as in, “to be in flux.”) All of these can be understood in the sense that, that which is loose flows — and all of these words flow in one way or another: liquids are fluid, you speak fluently, flushing water flows, money flows if you are affluent, etc.
The -x- in the original Latin tended to disappear into the English (hence leaving the vowels before and after, as in fluent or fluid) or became a -sh- sound. This is an example of the common pattern of the -sh- sounds mapping to the throat-clearing -j- in Spanish, with the fl-sh of flush mapping to the fl-j of flojo.
The “sh” sound — often represented in writing as an “x” — transformed in all different ways to the “j” letter (and the accompanying mouth-clearing sound, influenced by Arabic) as late Latin turned into Spanish. See lots of examples: sherry/jerez, for example.
Here’s another: the common Spanish word, dejar, meaning, “to leave to the side” or “to put down” or to “put away” or to just “let go.”
Dejare comes from the Latin laxare, meaning, “to loosen”. From this same root, we get a few English words — which did not go through the x-to-j transformation Spanish did including:
Jeringa, Spanish for Syringe, sounds like it has nothing in common with its English counter-part. But they are literally the same word.
The Latin sh- sound often evolved into the j- sound in Spanish — originally retaining the sh- sound but eventually, under Arabic’s influence, transforming to the throat-clearing sound we know and love.
This explains how both jeringa and syringe derive from the same root: the Latin siringa, itself from the Greek syringa. The sy- sound is a variation of the sh- sound and therefore the sy-r-n-g of syringe maps to the j-r-n-g of jeringa.